A mentally ill woman may not have been administered the drugs that killed her if blood tests had been carried out to establish if she could handle them, an inquest has ruled.

Barbara Norman, 53, died from heart failure as a result of having high levels of two anti-psychotic drugs in her system on July 7, 2006.

Following a three-day inquest at Flax Bourton Coroner's Court, a jury concluded that health workers may have decided not to administer the drugs to her at Lansdowne House, Warmley, if blood tests had been done to establish if her body could cope with them.

The jury found that the dose and combination of drugs given to Ms Norman would have been "acceptable in a patient with normal hydration and electrolyte levels".

But in its narrative verdict on the case, the jury ruled she had not been eating and drinking normally in the weeks leading up to her death and "concerns had been expressed".

The narrative verdict read: "No blood tests had been taken since Ms Norman had returned from Frenchay Hospital on the June 23. Had Ms Norman been transferred to Callington Road (a mental health unit in Bristol) it would have enabled blood tests to be taken. The results of these tests may have had an impact on the decision to administer thioridazine and olanzapine."

On Wednesday, the inquest heard a post-mortem examination concluded Ms Norman's body had been unable to cope with the amount and combination of thioridazine and olanzapine she had taken, which prompted her heart and respiratory system to fail.

Avon's deputy coroner Brian Whitehouse heard Ms Norman was to be transferred from Lansdowne House to Callington Road, a specialist psychiatric unit which could offer her more intensive treatment, but was taken to Frenchay Hospital by ambulance on July 7, 2006, when staff were unable to wake her.

She was pronounced dead on arrival at the hospital at 4am.

The inquest heard Ms Norman's family complained to Bath and North East Somerset Primary Care Trust, which was responsible for Ms Norman's care, arguing the tragedy could have been avoided.

In a letter to the trust read out at the inquest, Ms Norman's sister Wendy Ferrari said her sibling started to suffer problems in 2001 and then in 2005 when she was taken off the drug thioridazine, which had helped with her schizophrenia for 25 years without ill effects.

She said switching Ms Norman, who used to live in Knowle, between thioridazine and alternative drugs worsened her condition and culminated in her not walking or talking in the weeks leading up to her death.